Objectives have become widely used in various applications in private, commercial, as well as in industrial fields, and also in research and development. There are different types of objectives for the various applications that differ essentially in their geometry, as well as in the arrangement of the individual optical elements with their specific characteristics.
Objectives essentially consist of an arrangement of optical elements, which can be lenses, apertures and mirrors that are located at a distance with respect to each other along an optical axis. The individual optical elements are mounted in the outer mounting of an objective. The mounting of the individual optical elements can take place directly in the outer mounting; however, in particular in the case of higher demands, sub-mountings or inner mountings are used by means of which the optical elements are arranged in the objective.
In particular for industrial, as well as also for scientific optical applications, higher demands are made on the optical imaging quality of an objective. Frequently, for the examination of fine structures, such as integrated circuits, objectives are used as they are particularly well suited because of their imaging properties.
In these applications it is often required to image or illuminate individual areas on expanded objects, such as wafer surfaces, not orthogonally, but at a certain angle. Thereby, oftentimes as small an angle as possible is required between the optical axis of the objective and the wafer surface. However, the type of construction of known objectives, in particular their exterior dimensions and their working distance limits the incline of the objective, so that the desired small angles cannot be obtained with conventional objectives.